In the early 1990s in Rwanda, a popular radio station backed by Hutu extremists began broadcasting racist propaganda. The country was submerged in hateful rhetoric which denigrated the Tutsi minority as inyenzi, meaning cockroach. Leading up to the genocide that resulted in 800,000 deaths, the Rwandan newspapers published pictures that depicted Tutsis as cockroaches and snakes. When the killings began, Hutus were incited to “crush the cockroaches.”

This rhetoric, likening human beings to vermin, allowed the Hutu to dehumanize the Tutsis. This process of dehumanization removes moral and ethical boundaries that normally prevents people from killing each other. Dehumanization is an effective and ancient strategy used to facilitate violence and genocide.

Alarmingly, in 2017, just over 100 days into his presidency, Trump is utilizing this same dehumanizing rhetoric. On Saturday, instead of attending the White House Correspondents Dinner, Trump chose to hold a rally in Pennsylvania. In his speech to supporters, Trump revived an old campaign favorite. He read the poem “The Snake”, a parable about the dangers of welcoming strangers into your home.

In the poem, which Trump dedicates to “General Kelly, to the border patrol, and to the ICE agents”, a woman, the subject of the poem, comes across a dying snake. The “tender-hearted” woman brings the snake into her home, giving it “some honey and some milk.” The snake, revived by the woman’s generosity, responds to this act of kindness by biting the woman with its poisonous fangs. The woman cries out and asks “Why?” Trump’s snake sneers, “‘Oh shut up, silly woman… You knew damn well I was a snake before you took me in.’”

Before he began reading the poem, Trump made sure the metaphor was not lost on his audience: “I thought of it having to do with our borders and people coming in, and we know what we’re going to have, we’re going to have problems.”

Given his poor grasp of history, perhaps Trump does not understand the thick historical roots of dehumanizing rhetoric that targets minorities and “outsiders”. Perhaps Trump has never reflected on the fact that the Nazis also weaponized language, churning out propaganda that depicted Jews as rats, leeches, lice, bacteria, or other vectors of contagion. The Nazis even had a word that described such people: Untermenschen – “subhuman.”

This process of dehumanization, mastered by the Nazis and practiced by countless groups of people throughout history, stigmatizes an entire group of people as evil, morally inferior, and not fully human. Dehumanization overrides psychological restraints against violence and aggression: While it is unacceptable to kill a human being, exterminating rats is perfectly acceptable.

Scholar David Livingstone Smith wrote, “Dehumanization isn’t a way of talking. It’s a way of thinking—a way of thinking that, sadly, comes all too easily to us. Dehumanization is a scourge, and has been so for millennia. It acts as a psychological lubricant, dissolving our inhibitions and inflaming our destructive passions. As such, it empowers us to perform acts that would, under other circumstances, be unthinkable.”

Dehumanization is so powerful that it changes behavior. At Stanford, Albert Bandura discovered that when participants overhear an authority figure call another study subject “an animal,” they’re more likely to give that subject a painful shock. Under the process of dehumanization, hateful words are transformed into hateful action.

Dehumanization allowed the Hutus to hack their Tutsi neighbors to death with machetes. Dehumanization is the rhetoric that birthed the Holocaust. Dehumanization is an integral step on the road to mass violence.

According to Gregory H. Stanton, expert in genocide studies, there are ten stages of genocide. The fourth stage of genocide is dehumanization. At this stage “one group denies the humanity of the other group. Members of it are equated with animals, vermin, insects or diseases. Dehumanization overcomes the normal human revulsion against murder. At this stage, hate propaganda in print and on hate radios is used to vilify the victim group.”

“Dehumanization overrides psychological restraints against violence and aggression: While it is unacceptable to kill a human being, exterminating rats is perfectly acceptable.”

While Trump may not know this history, he has demonstrated a keen understanding of the power of rhetoric. Make no mistake, Trump’s allegory of the snake is language designed to dehumanize immigrants and refugees. By depicting these vulnerable populations as “vicious” snakes, Trump has hijacked the same psychological processes that fueled past atrocities.

As the president of the United States, Trump’s words matter, more than anyone else’s in the world. When Trump dehumanizes entire groups of people, as he has done throughout the campaign and the early days of his presidency, he is sending very loaded messages to his supporters. Trump’s “vicious snake” is a warning to white Americans: “You are not safe. Muslims, Mexicans, and outsiders are devious infiltrators, who will not rest until they destroy us and our way of life. I alone can protect you.”

While I do not believe we are on the verge of genocide, Trump’s dehumanizing rhetoric has real consequences. Since the start of the 2016 campaign, hate crimes have skyrocketed; reports of Muslim hate crimes are at their highest levels since 2001. Across the country, mosques have been set on fire. In schools, children chant “Build that wall!” to harass and terrify their fellow students. These incidents do not happen in a vacuum. This rhetoric comes directly from the top, from a president who uses his bully pulpit far too literally.

Watching Trump read “The Snake” was disturbing for many reasons, but I was particularly struck by the reaction of the audience. As Trump read the poem, his supporters grinned and cheered loudly; some even knew the story by heart, reciting the words with him.

This reaction is unsurprising. According to a 2016 study, researchers found that blatant dehumanization of Muslims and Mexican immigrants was strongly correlated with Trump support. In the journal Personality and Social Psychology Bulletin, researchers concluded that the data is “consistent with the idea that support for some of the Republican candidates (and Trump in particular) comes not despite their dehumanizing rhetoric but in part because of it.”

These findings are significant. They indicate that the process of dehumanization is well under way. By exploiting already existing tensions, Trump feeds off of his supporters negative feelings towards “outsiders.” By engaging in dehumanizing rhetoric, Trump receives the only thing he’s ever wanted: praise and adoration. It doesn’t matter whether or not Trump truly believes that Muslims and Mexicans are “vicious snakes”.

By legitimizing the process of dehumanization, Trump has poured gasoline on a fire. His most rabid and white supremacist supporters look to Trump to validate their hateful ideologies. As evidenced by the results of the 2016 election, Trump has found dehumanization to be a potent tool for political mobilization. He will continue to exploit this ancient tactic, while American civil society deteriorates and minority groups live in terror.

As I watched Trump’s reading of “The Snake”, I noticed a child in the crowd behind Trump’s podium. He stood in rapt attention, his mouth hanging slightly open, never looking away from the president. As the child listened wide-eyed to the words dripping with hatred, the violent process of dehumanization was underway: You knew damn well I was a snake before you took me in.

Words are powerful. As history has proven time and time again, dehumanization is the first step on the road to unimaginable cruelties. Philosopher Sam Keen writes, “We think others to death and then invent the battle-axe or the ballistic missiles with which to actually kill them.” It is incumbent that we identify and condemn dehumanizing rhetoric, especially when our leaders engage in it. Language designed to do harm has no place in American political rhetoric.